Classic Inlines
603 W Pecos Ave
Mesa, AZ 85210

Harmonic Damper/Balancer

The most common items over looked during assembly and installation of a rebuilt motor, are the motor mounts, transmission mounts, and the harmonic damper (balancer). Motor mounts are commonly bonded together using a variety of rubber compounds, while most OEM dampers utilize an elastomer (rubber) inertia ring, which is pressed into place. Over the years the rubber compounds dry out and become brittle, eventually resulting in product failure. In most cases these failures lead to un-necessary and costly repairs, and they can be dangerous, even life threatening, if they occur at the wrong moment. Therefore it is essential to thoroughly clean and inspect these parts prior to reuse. If the rubber or metal parts show signs of cracking, excessive wear, or have small pieces missing, they need to be rebuilt or replaced.

Selecting the right damper for your application.

To select the proper damper, one first needs to understand it's purpose. A harmonic damper is often referred to as a balancer, which seems to suggest that the unit “balances” the engine. However it's actual function is to dampen torsional vibrations which occur in the crankshaft. These vibrations are the result of the combustion process, or more accurately the sudden reversal of load on the pistons, connecting rods, and the crankshaft. The subsequent relaxation of the load, following the combustion event, causes a deflection or flexing of the crankshaft. At certain rpm ranges these oscillations come into phase with each other, which generates potentially harmful and damaging torsional peaks within the crankshaft. This oscillating vibration, which results from the reciprocating load changes, will remain in force until it is dissipated by internal friction and/or damping. Unless the amplitude of these torsional vibrations is controlled, major damage can occur to engine components, such as rapid wear of the timing gears, stretching or breakage of the timing chain, pitting or cupping of the camshaft and lifters, broken valve springs and/or valve train failure, or excessive wear of the engine bearings. In extreme situations these uncontrolled torsional vibrations can lead to loose or broken flywheel bolts and/or crankshaft failure, which may result in serious safety consequences.

As we stated earlier, most OEM and/or rebuilt dampers utilize an elastomer (rubber) inertia ring, which is pressed into place. While this is adequate for low revving engines, it won't handle the higher torque and revolutions of a performance motor. Using an old worn out damper, or an inadequate damper for the application, usually results in the spinning of the inertia ring, which in turn results in the loss of timing accuracy and eventual component separation. Even some of the more costly steel or alloy performance dampers use a similar rubber insert, which will break down over time, in much the same way as standard damper.

Classic Inlines offers three different harmonic dampers or balancers; Rebuilt, Performance Street, Performance Plus. All of our dampers are bonded, offering superior strength and durability over stock EOM dampers. Which one you use depends on the performance level of your motor. The Rebuilt balancer are great for stock or mild performance engines which normally operate under 5000 rpm. Our Performance Street balancers are designed for performance inlines that spin up to 6500 rpm. Our Performance Plus balancers are similar to the Performance Street balancers, also good to 6500 rpm, however they feature an additional clear hard-coat for increased durability and appearance.

For engines that make over 400HP, or those that spend time on the strip, you may need an SFI Certified balancer. While Classic Inlines doesn't carry them, they can be purchased from ATI Performance Products. They don't show them in their catalog, but they will custom build one for $250-300 bucks, which isn't bad for a custom balancer. Eventually we hope to offer SFI Certified balancers, but that's down the road a bit.

Our Stock Rebuilt balancer are disassembled, cleaned, and inspected for defects. Including stripped bolt holes, worn or cracked keyways, cracked center webbing, and there overall condition. Once they pass inspection they prepared for assembly, which includes resetting the timing marks using a superior laser aligning process. The balancers are then injected with a high-temperature, high-strength silicone rubber that is platinum cured for a stronger bond. This new silicone rubber compound is capable of withstanding temperatures in excess of 450 degrees, and will hold up to pressures as high as 770 psi. All stock Rebuilt Balancers carry the manufacturers "Three Year Limited Warranty".

The limiting factor with rebuilt balancers, is that they use the stock cast iron parts, which can crack in the keyway and/or center webbing. While the bonding process is far superior to new OEM balancers, the stock gray cast iron parts limit the revolutions to 5000 rpm. Our Performance Street balancers solve this problem by using new metal components, which are made from high strength nodular iron. Next, a state of art bonding process is utilized, which uses extreme heat and pressure to positively bond the dampening compound to the new metal components. By using nodular iron and a superior bonding process, the common failures which are associated with stock and/or rebuilt balancers are eliminated, thereby increasing the performance capabilities to 6500 rpm. Performance Street balancers carry the manufacturers "One Year Limited Warranty". While these balancers may look like a stock balancer, I can assure you they are not. The quality is far superior to that of a stock replacement balancer (se chart below).

Our Performance Plus balancers, which are similar to our Performance Street balancers, feature an additional clear hard-coat finish for increased durability and appearance. Offering unmatched reliability for engines with increased horsepower and torque, up to 6500rpm, they carry the manufacturers "Two Year Limited Warranty".

While our bonded Rebuilt Balancers have four times the strength of inserted rubber, in push apart and torque tests, our Performance Street balancers have nine times the strength of inserted rubber and two and a half times that of rebuilt balancers.
SFI Certification

The SFI Foundation, Inc. is a non-profit organization which was established to issue and administer industry standards for specialty performance automotive and racing equipment. The SFI Spec. 18.1 provides a set of minimum requirements, that the manufacturer must comply with when producing crankshaft vibration dampers. The standards were introduced to ensure safety on the track, where certain racing classes require an SFI Certified damper, as specified by the sanctioning body. The specifications stipulate the minimum mechanical properties for the steel used in the construction, the requirement that the outer ring must be retained in the event of a failure, and that the damper is subjected to spin test of 12,500 rpm for a minimum of one hour.
Balancer Replacement

1)  Remove the balancer/damper carefully using a Professional damper removal tool.

2)  Clean the crank snout with very fine abrasive paper to ensure no burrs exist.

3)  Check the bore of the balancer to ensure there is no paint residue, if required clean
the area with very fine abrasive paper.

4)  Re-check the sizes, particularly the height of the crankshaft key, as some aftermarket keys do not meet OEM specs.

5)  Prior to installation heat the balancer in boiling water for 15 minutes, or place it in a preheated oven at a low temperature (max 250 deg F or 120 deg C) for 15 minutes.

6) Coat the crankshaft snout and inside diameter of the damper with an anti-seize compound or moly grease to prevent galling during installation.

7) Remove from oven using insulated heatproof gloves, oil the crank snout and promptly install using a professional damper installation tool.

Note: If you don't have a damper installation tool, stop by your local hardware store and pick up a 4-5" long bolt, a fender washer, and a nut, which are the same diameter and thread as your original damper bolt. Spin the nut all the way on to the long bolt, then slip on the fender washer, and finally your original damper washer. Once the heated damper is fitted onto the crank snout as far as possible (without hammering) thread the bolt assembly into the crank by hand. Make sure it goes into the crank at least an inch to prevent the threads from stripping (it takes a lot of force to install the damper). Spin the nut until the washer is snug against the balancer, then tighten the nut with a box wrench until the balancer is fully seated. Remove the bolt assembly and install the original bolt and washer, then torque to the proper torque specifications.

NOTE: Never hammer a balancer into place, as it can easily damage the crankshaft thrust bearings and seals.

Core Charge

All Classic Inlines balancers include a core charge in the purchase price, which may be refundable. Please remember to send in your core once you receive your new or rebuilt balancer. Not only is it required for a core refund, we need them so we can keep the process going. Without cores, we have nothing to rebuild for the next customer. Thank you

For more information, please read our Core Charge Refund policy.

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